Disproportionate thickening of the ventricular septum (a finding characteristic of hearts with genetically transmitted ASH) was present in about 10 percent of hearts from patients with a variety of congenital or acquired heart diseases. The absence of disorganized myocardial cells in the ventricular septum of these patients and the rare occurrence of disproportionate septal thickening in their close relatives suggests that the disproportionate septal thickening is probably secondary to their basic heart condition.